void main(List<String> args) {
  // 泛型
  Map<String, int> zs = {
    "age": 18,
  };
  zs.forEach((key, value) {
    print("$key:$value");
  });
  sayHello(1230);
  sayHello("1230");
}

T sayHello<T>(T name) {
  return name;
}
